Use active state on touch start for tray icons

ash/system/overview/overview_button_tray.h

Index: ash/system/overview/overview_button_tray.h
diff --git a/ash/system/overview/overview_button_tray.h b/ash/system/overview/overview_button_tray.h
index 32feb0c60b4ecfbc2a5f1b421a4a1a28011a49ef..fe33ada554116dfe27c11c53aeb23d38eb32e554 100644
--- a/ash/system/overview/overview_button_tray.h
+++ b/ash/system/overview/overview_button_tray.h
@@ -6,7 +6,6 @@
 #define ASH_SYSTEM_OVERVIEW_OVERVIEW_BUTTON_TRAY_H_
 
 #include "ash/ash_export.h"
-#include "ash/shell_observer.h"
 #include "ash/system/tray/tray_background_view.h"
 
 namespace views {
@@ -20,8 +19,7 @@ namespace ash {
 // This hosts a ShellObserver that listens for the activation of Maximize Mode
 // This tray will only be visible while in this state. This tray does not
 // provide any bubble view windows.
-class ASH_EXPORT OverviewButtonTray : public TrayBackgroundView,
-                                      public ShellObserver {
+class ASH_EXPORT OverviewButtonTray : public TrayBackgroundView {
  public:
   explicit OverviewButtonTray(StatusAreaWidget* status_area_widget);
   virtual ~OverviewButtonTray();